entrifugal switch assembly for a motor starting circuit

ABSTRACT

A centrifugal switch assembly for a motor having a starting circuit including a basket shaped actuator normally spring biased into engagement with switch contacts maintaining the starting circuit closed during static and motor low speed conditions. The switch actuator is mounted in a support member providing guide slots preventing rotation of the actuator relative to rotating motor components while being spring biased to the switch closed position. Centrifugal force responsive weights are pivotally mounted in the support member and engage the basket switch actuator moving it against the force of the biasing spring opening the switch contacts when the motor reaches a predetermined speed. The components of the actuator assembly are concentrically positioned upon the motor shaft adjacent the rotor and inwardly of the usual lubricating assembly in a manner without increasing the axial length of the motor.

United States Patent [1 1 Fannin et al.

1 Apr. 29, 1975 CENTRIFUGAL SWITCH ASSEMBLY FOR A MOTOR STARTING CIRCUIT[75] Inventors: Wayne V. Fannin; Edwin H.

Halsted, both of Dayton. Ohio [73] Assignee: General Motors Corporation,

Detroit. Mich.

[22] Filed: Apr. 11, 1974 [21] Appl. No.1 460,042

Primary E.\'aminerG. Z. Rubinson Altornev. Agent, or" FirmCharles R.Engle [57] ABSTRACT A centrifugal switch assembly for a motor having astarting circuit including a basket shaped actuator normally springbiased into engagement with switch contacts maintaining the startingcircuit closed during static and motor low speed conditions. The switchactuator is mounted in a support member providing guide slots preventingrotation of the actuator relative to rotating motor components whilebeing spring biused to the switch closed position. Centrifugal forceresponsive weights are pivotally mounted in the support member andengage the basket switch actuator moving it against the force of thebiasing spring opening the switch contacts when the motor reaches apredetermined speed. The components of the actuator assembly areconcentrically positioned upon the motor shaft adjacent the rotor andinwardly of the usual lubricating assembly in a manner withoutincreasing the axial length of the motor.

3 Claims, 4 Drawing Figures CENTRIFUGAL SWITCH ASSEMBLY FOR A MOTORSTARTING CIRCUIT This invention relates to centrifugally actuatedswitches and more specifically to an improved centrifugal switchassembly for electric motors controlling a starting circuit therein.

Centrifugally actuated switches are commonly employed in single phase ACinduction motors which are used in industrial and household devicesincluding appliances such as, clothes washers and dyers, dishwash ers,garbage disposals, etc. These motors typically include a main windingand a starting winding which are energized when the motor is turned on.A centrifugal switch mechanism disconnects a starting winding when themotor has reached a predetermined speed and it is no longer desirable tomaintain the starting winding energized.

Among the significant features of centrifugal switch mechanisms are themounting arrangements and utilization of space within the motor housingwithout changing the size or shape of the electric motor. It isparticularly desirable that the centrifugal switch assembly include aminimum of components so that the switch is reliable. easily assembled,and is readily serviceable so that the switch mechanism can be easilymanufactured and assembled in the motor housing.

In accordance with the present invention, a centrifugally actuated motorswitch assembly includes a support member containing a centrallydisposed aperture for concentrically positioning it upon the motor shaftand it includes diametrically opposed axially extending flanges. Theaxially extending flanges contain guide slots receiving guide memberson'a basket shaped switch actuator which is slidably mounted relative tothe support member and is also concentrically positioned on the motorshaft. A conical coil spring likewise is concentrically positioned onthe motor shaft between the support member and the switch actuatornormally biasing the switch actuator outwardly of the support member.

A pair of conductive leaf spring switch arms are rigidly secured in aninsulating block attached to the motor housing. The switch arms havealigned contacts secured thereon and are normally biased open by theirinherent spring characteristics. The basket shaped switch actuatorincludes a circumferential radially extending flange at its outerperiphery terminating in an annular switch actuating rim. The coilspring between the support member and the switch actuator normallybiases the rim into engagement with the leaf spring arms retaining thecontacts in engagement normally closing the starting circuit. A pair ofweight members include a pair of spaced arcuate fingers engagingsupporting shoulders on the basket shaped switch actuator. They alsoengage spaced axially extending mounting lugs on the support memberflanges pivotally supporting the weights in the assembly. The weightmembers are responsive to centrifugal force and pivot upon the supportmember flanges depressing the basket shaped switch actuator against theforce of the coil spring moving the annular ring out of engagement withthe leaf spring arms and opening the starting circuit when the motorreaches a predetermined speed.

. Accordingly, a primary object of this invention is the provision of animproved centrifugal switch assembly for an electric motor that iscompactly mounted internally of the motor in a manner requiring aminimum of housing .-;pace.

Another object of this invention is the provision of a centrifugalswitch actuator assembly for an electric motor wherein the actuatorassembly is mounted concentrically about the motor shaft inwardly of theusual lubricating assembly provided in the area where the shaft isrotatably mounted in the motor housing, the actuator assembly includinga basket shaped actuator guided and slidably mounted within a supportmember for positive actuation in response to centrifugal forces wherebyit opens a starting circuit when the motor attains a predeterminedspeed.

A further object of this invention is the provision of a centrifugallyresponsive switch actuator assembly within a motor housing positionedconcentrically upon the motor shaft axially between the rotor and alubricating oil well assembly in the motor housing so as to takeadvantage of available space without increasing the axial length of themotor housing, the actuator assembly including a support member havingdiametrically opposed axially extending flanges containing guide slotsreceiving guide lugs on a basket shaped switch actuating member normallyspring biased to close contacts on leaf spring switch members, and apair of weights being pivotally mounted in the support member flanges inengagement with the switch actuating member, the weights moving radiallyoutwardly in response to motor speed thereby moving the switch actuatorinwardly within the support member, opening the switch contacts andconsequently the starting circuit when the motor attains a predeterminedspeed.

The novel features which we believe to be characteristic of ourinvention are set forth with particularity in the appended claims. Ourinvention itself, however, both as to its organization and method ofoperation, may be best understood by reference to the followingdescription taken in connection with the accompanying drawings in which:

FIG. 1 is a side elevational sectional view of an electric motoremploying a centrifugal switch actuating assembly in accordance with thepresent invention.

FIG. 2 is an exploded perspective view illustrating the components ofour centrifugal switch actuating assembly in aligned positions removedfrom the electric motor.

FIG. 3 is a fragmentary sectional view taken on line 33 of the switchactuator shown in FIG. 2 with the remaining components in assembledrelationship illustrating the switch actuating mechanism in acentrifugal force operated position.

FIG. 4 illustrates an electrical schematic diagram including the switchcontacts actuated by our centrifugal force responsive mechanism.

Referring now to FIG. 1, an electric motor 10 of a single phase ACinduction motor type includes a motor housing 12, a stator 14, and arotor 16 affixed to a shaft 18 for rotation therewith. The stator 14 issupported within housing 12 and includes a stator winding 20 comprisinga main winding 22 and a starting winding 24 shown schematically in FIG.4. The motor housing 12 is substantially cylindrical in form andincludes end frames 26 and 28 enclosing opposite ends thereof. The endframes 26 and 28 include annular bearing supports 30 and 32 whichcontain bearing assemblies 34 and 36, respectively. The shaft 18includes a forward portion 38 rotatably supported in bearing 34 whichprovides an output driving connection for the motor while a rearwardportion 40 of the motor shaft 18 is supported by bearing 36. In apreferred embodiment, the shaft 18 is vertically disposed although, ofcourse, the shaft can be disposed horizontally without departing fromthe principal features of the present invention.

The rotor 16 includes a plurality of squirrel cage bars, not shown,which extend through the rotor and electrically connect with a pair ofend rings 42 and 44 disposed on opposite ends of the rotor 16. The endrings 42 and 44 can be made of a cast aluminum or other suitableconductive material and electrically interconnect with the squirrel cagebars, as previously indicated, in a well known manner. The end rings 42and 44 have fan blades 46 cast integrally therewith for circulating airthrough the interior of housing 12 as the shaft 18 rotates. The fanblades 46 extend axially from the end rings 42 and 44 and arecircumferentially spaced so that open spaces between the blades areformed radially of the shaft 18.

The annular bearing supports 30 and 32 define cavities 48 and 50 eachcontaining a quantity of porous material 52 impregnated with a lubricantso as to effectively lubricate the shaft 18 in the areas of bearings 34and 36 during operation of the motor. The cavities 48 and 50 aresubstantially enclosed at the interior end thereof by thrust washers 54secured to the annular bearing supports'30 and 32 and extending intoengagement with the outward side of annular flanges S6 attached to theshaft 18.

A centrifugal switch actuating assembly 58, con structed in accordancewith my invention, is positioned between the rotor 16 and the annularflange 56 near the driving end 38 of shaft 18. The switch actuatingassembly 58 includes a support member 60 containing a central aperture62 defined by an annular flange 64 which provides for the concentricpositioning of the support 60 upon shaft 18 adjacent rotor 16 inengagement with end ring 42. The annular flange 64 has an inner surfaceengaging a splined surface 19 on shaft 18 providing a driving connectiontherebetween. The support member 60 includes diametrically oppositelypositioned axially extending flanges 66 which terminate in I radiallyextending flanges 68 being deformed to include walls 86 which connectwith bottom surface 80 via an integral extended portion 88 and connectwith the switch actuating rim 82 by means of an integral radiallyextending flange 90. The vertical walls 86 are cut away to providerounded shoulders 92 on either side of the vertical wall as isspecifically illustrated in FIG. 2.

A pair' of centrifugal force responsive weights 94 include spacedarcuate fingers 96 at either end of the top edge defining a notchtherebetween. The axially extending flanges 66 of the support member 60are of a width sufficient to permit positioning of the arcuate fingers96 of weights 94 on either side thereof adjacent the verticallyextending lugs 70. Likewise, the vertical wall 86 of the basket switchactuator 78 is of a width sufficient to permit positioning of thearcuate fingers 96 upon rounded shoulders 92 so that'in an assembledrelationship the weights 94 are operative to pivot relative to thesupport member and move the switch actuator 78 against the force ofspring 74 as will be later described with respect to operation of ourimproved centrifugal switch actuating mechanism.

The motor housing 12 has an insulating block 100 secured thereto bymeans of a rivet 102, shown in FIG. 1. The insulating block 100 isnotched at 104 and 106 and leaf spring switch actuating members 108 and110 are respectively secured therein as best shown in FIG. 2. The leafspring members 108 and 110 have contacts 112 and 114 secured thereon inaxial alignment for engagement in a switch closed position. The switchactuating arms 108 and 110 are connected in series electric circuitrywith one power line 23 and the starter winding 24, as schematicallyillustrated in FIG. 4.

The basket switch actuator 78 includes integral axially extending guidelugs 116 extending outwardly of the vertical walls 86 which are slidablyreceived within notches 76 in the axial-extending flanges 66 of supportmember 60. This arrangement provides for sliding movement of the basketmember 78 relative to the support member 60 as influenced by the coilbiasing spring 74 while preventing relative rotation between support 60and actuator 78. As previously mentioned, the annular flange 64 of thesupport member 60 includes an inner surface engaging the splined surface19 formed upon the shaft 18 drivingly connecting the support 60 withshaft 18. In this manner the shaft 18 is effective to rotate the supportmember 60 while the guide members 116 residing in slots 76 provide adriving connection between the support member and the basket member 78so that it is positively rotated with rotor 16 during operation of themotor. This arrangement is necessary to retain the switch actuatorassembly in a fixed angular position out of interference with thecooling fan blades 46 on the end ring 42.

In operation, with the motor in a static condition or in a low speedinitial operating condition, the coil spring 74 is effective to maintainthe basket switch actuator 78 in an extended position moving contact 114into engagement with contact 112 maintaining the circuit throughstarting winding 24 closed. The extended movement of the basket switchactuator 78 is limited by engagement of rounded shoulders 92 of thebasket switch actuator 78 with arcuate portions 96 of weights 94 whichin turn has the top edge of notch 98 in engagement with the radiallyextending flanges 68 of support member 60, as illustrated in FIG. '1.When the motor attains a predetermined speed, the weights 94 pivotradially outwardly with the arcuate portions 96 remaining in engagementwith the vertically extending lugs 70 while simultaneously continuallyengaging cuit through the starting winding 24 is opened arid the. motorcontinues to operate by means of a closed (:ircuit' through main winding22.

From the above description it is apparent that our invention provides acompact centrifugal force responsive switch actuating mechanism whichfits within a conventional motor structure without increasing the axiallength thereof. A conventional motor structure can be slightly modifiedto accommodate this arrangement, the only necessity being that a splinedsurface 19 be provided upon the motor shaft 18. The incorporation ofguide members 116 on the basket shaped switch actuator 78 insuresrotation of the basket member with rotor 16 while preventing undesirabletilting or binding of the components so that it can readily move axiallyrelative to the shaft 18 under the influence of coil spring 74 or inresponse to centrifugal forces sensed by the weights 94. Also,engagement of guide members in support member slots 76 fixes the radialposition of the switch actuator 78 relative to the rotating motorcomponents permitting unobstructed motor operation.

While we have shown and described a particular embodiment of the presentinvention it will, of course, be understood that various modificationsand alternative constructions thereof may be made without departing fromthe true spirit and scope of our invention and that we intend by theappended claims to cover all such modifications and alternativeconstructions as fall within the true spirit and scope of our invention.

We claim:

1. A centrifugal switch actuator assembly for an electrical motorincluding a main winding; a starting winding; a shaft; a housingenclosing said windings and rotatably supporting said shaft; and a rotorfixedly mounted to said shaft for rotation within said housing; saidcentrifugal switch actuator assembly comprising: an electrical switchassembly mounted on said housing and including first and second contactshaving mutually engaging and disengaging positions; a series electricalcircuit including said starting winding and said first and secondcontacts; a support member containing a centrally positioned aperturereceiving said shaft; said support member including axially extendingflanges; a basket-shaped switch actuator mounted within the flanges ofsaid support member; guide means on both said support flanges and saidbasket switch actuator cooperating and preventing rotation of saidactuator relative to said support member while guiding axial movement ofsaid actuator relative to said support member; a peripheral rim on saidswitch actuator positioned for axial movement between a switch contactengaged position and a switch contact disengaged position; a coil springpositioned between said support and said actuator normally biasing thebasket actuator away from said support to a contact engaged position;and a plurality of weights pivotally attached to said basket switchactuator whereby said weights respond to the centrifugal forcesdeveloped at a predetermined motor speed moving said actuator againstthe force of said biasing spring positioning said rim out of engagementwith contacts opening the circuit to said starting winding.

2. A centrifugal switch actuator assembly for an electrical motorincluding a main winding; a starting winding; a shaft; a housingenclosing said windings and rotatably supporting said shaft; and a rotorfixedly mounted to said shaft for rotation within said housing; saidcentrifugal switch actuator assembly comprising: an electrical switchassembly mounted on said housing and including first and second contactshaving mutually engaging and disengaging positions; a series electricalcircuit including said starting winding and said first and secondcontacts; a support member containing a centrally positioned aperturereceiving said shaft; diametrically opposed flanges extending axially ofsaid motor and terminating in radially extending flanges on said supportmember; a basket-shaped switch actuator; said switch actuator includinga bottom portion; an annular peripheral rim; a plurality of angularlyextending web members securing said rim to said base; diametricallyopposed vertical walls integral with said switch actuator extendingbetween the bottom of said actuator and said annular rim; a guide lug oneach of said vertical walls; said axially extending support flangescontaining guide notches slidably receiving said lugs; a coil springconcentrically positioned about said shaft engaging said support memberand the bottom of said switch actuator normally biasing said switchactuator away from said support member into a position engaging saidfirst and second contacts; said vertical walls of said switch actuatoreach including spaced shoulders; said radial flanges of said supportmember each including spaced axially extending lugs; and two weightmembers each comprising a pair of spaced arcuate fingers engaging saidshoulders on said walls and being retained by said axially extendinglugs on said support member whereby a predetermined centrifugal forceresulting from a predetermined motor speed causes said weights to moveradially outward forcing said basket shaped switch actuator against theforce of said coil spring moving said annular rim out of engagement withone of said switch contacts permitting disengagement of said first andsecond contacts thereby opening the series circuit to said startingwinding.

3. A centrifugal switch actuator assembly for an elec trical motorincluding a main winding; a starting winding; a shaft; a housingenclosing said windings and rotatably supporting said shaft; an annularflange fixed on said shaft; a thrust washer secured to said housing incontact with the outer face of said flange effectively sealing theinterior of said housing from the atmosphere; and a rotor fixedlymounted to said shaft for rotation within said housing; said centrifugalswitch actuator assembly comprising: an electrical switch assemblymounted on said housing; said switch assembly including first and secondleaf spring switch members; a contact on each of said leaf springmembers; and leaf spring members normally being inherently springbiasedto a circuit open position; a series electrical circuit including saidstarting winding and said leaf spring members; a support membercontaining a centrally positioned aperture providing for the positioningof said support member concentrically upon said shaft between said rotorand the inner side of said shaft annular flange; diametrically opposedflanges extending axially of said motor and terminating in radiallyextending flanges on said support member; a basket-shaped switchactuator; said switch actuator including a base; an annular peripheralrim secured to said base by a plurality of angularly extending webmembers; diametrically opposed vertical walls integral with said switchactuator extending between the base of said actuator and said annularrim; a guide lug on the outer side each of said vertical walls; saidaxially extending support flanges containing guide notches slidablyreceiving said lugs; the base of said actuator containing an aperturereceiving said motor shaft; said lugs in said notches and said verticalwalls in conjunction with said axially extending flanges all cooperatingfor concentrically positioning said basketshaped switch actuator uponsaid shaft; a coil spring concentrically positioned about said shaftengaging said support member and the base of said switch actuatornormally biasing the switch actuator away from said support member intoa position engaging the contacts on said first and second leaf springmembers; said vertical walls of said switch actuator each includingspaced shoulders; said radial flanges of a said support member eachincluding spaced axially extending lugs; and two weight members eachcomprising a pair of spaced arcuate fingers engaging said shouldersUNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENT NO. I 3,881, 143 DATED April 29, 1975 INVENTORG) 1 Wayne V.Fannin and Edwin H. Halsted It is certified that error appears in theabove-Identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 11, "dyers" should read dryers Column 3, line 64, after"notch" insert 98 Column 6, line 46, after "members: change "and" tosaid Signed and Scaled this nineteenth D y f August 19 5 [SEAL] I Arresr:

RUTH (I. MASON Amnwrmg Officer C. MARSHALL D'AN'N ('ummissr'uncrnflalenrs and Trademarks UNITED STATES PATENT AND TRADEMARK OFFICE@ER'HHCATE Qt QQRRECHQN PATENT NO. 3 ,881,143

DATED April 29,, 1975 lNVEWOWS) Wayne V, Fannin and Edwin H. Halsted Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column l line 1.1 "dyers" should read dryers Column 3,, line 64, after"notch" insert 98 Column 6 line 46,, after "members? change "and" tosaid gigned and eae Item's [SEAL] Arrest:

RUTH C. MASON Arms-1mg ()j/r'rcr C. MARSHALL D'AN'N (nmmi'ssrmzernj'larenrs and Tradem arks

1. A centrifugal switch actuator assembly for an electrical motorincluding a main winding; a starting winding; a shaft; a housingenclosing said windings and rotatably supporting said shaft; and a rotorfixedly mounted to said shaft for rotation within said housing; saidcentrifugal switch actuator assembly comprising: an electrical switchassembly mounted on said housing and including first and second contactshaving mutually engaging and disengaging positions; a series electricalcircuit including said starting winding and said first and secondcontacts; a support member containing a centrally positioned aperturereceiving said shaft; said support member including axially extendingflanges; a basket-shaped switch actuator mounted within the flanges ofsaid support member; guide means on both said support flanges and saidbasket switch actuator cooperating and preventing rotation of saidactuator relative to said support member while guiding axial movement ofsaid actuator relative to said support member; a peripheral rim on saidswitch actuator positioned for axial movement between a switch contactengaged position and a switch contact disengaged position; a coil springpositioned between said support and said actuator normally biasing thebasket actuator away from said support to a contact engaged position;and a plurality of weights pivotally attached to said basket switchactuator whereby said weights respond to the centrifugal forcesdeveloped at a predetermined motor speed moving said actuator againstthe force of said biasing spring positioning said rim out of engagementwith contacts opening the circuit to said starting winding.
 2. Acentrifugal switch actuator assembly for an electrical motor including amain winding; a starting winding; a shaft; a housing enclosing saidwindings and rotatably supporting said shaft; and a rotor fixedlymounted to said shaft for rotation within said housing; said centrifugalswitch actuator assembly comprising: an electrical switch assemblymounted on said housing and including first and second contacts havingmutually engaging and disengaging positions; a series electrical circuitincluding said starting winding and said first and second contacts; asupport member containing a centrally positioned aperture receiving saidshaft; diametrically opposed flanges extending axially of said motor andterminating in radially extending flanges on said support member; abasket-shaped switch actuator; said switch actuator including a bottomportion; an annular peripheral rim; a plurality of angularly extendingweb members securing said rim to said base; diametrically opposedvertical walls integral with said switch actuator extending between thebottom of said actuator and said annular rim; a guide lug on each ofsaid vertical walls; said axially extending support flanges containingguide notches slidably receiving said lugs; a coil spring concentricallypositioned about said shaft engaging said support member and the bottomof said switch actuator normally biasing said switch actuator away fromsaid support member into a position engaging said first and secondcontacts; said vertical walls of said switch actuator each includingspaced shoulders; said radial flanges of said support member eachincluding spaced axially extending lugs; and two weight members eachcomprising a pair of spaced arcuate fingers engaging said shoulders onsaid walls and being retained by said axially extending lugs on saidsupport member whereby a predetermined centrifugal force resulting froma predetermined motor speed causes said weights to move radially outwardforcing said basket shaped switch actuator against the force of saidcoil spring moving said annular rim out of engagement with one of saidswitch contacts permitting disengagement of said first and secondcontacts thereby opening the series circuit to said starting winding. 3.A centrifugal switch actuator assembly for an electrical motor includinga main winding; a starting winding; a shaft; a housing enclosing saidwindings and rotatably supporting said shaft; an annular flange fixed onsaid shaft; a thrust washer secured to said housing in contact with theouter face of said flange effectively sealing the interior of saidhousing from the atmosphere; and a rotor fixedly mounted to said shaftfor rotation within said housing; said centrifugal switch actuatorassembly comprising: an electrical switch assembly mounted on saidhousing; said switch assembly including first and second leaf springswitch members; a contact on each of said leaf spring members; and leafspring members normally being inherently spring-biased to a circuit openposition; a series electrical circuit including said starting windingand said leaf spring members; a support member containing a centrallypositioned aperture providing for the positioning of said support memberconcentrically upon said shaft between said rotor and the inner side ofsaid shaft annular flange; diametrically opposed flanges extendingaxially of said motor and terminating in radially extending flanges onsaid support member; a basket-shaped switch actuator; said switchactuator including a base; an annular peripheral rim secured to saidbase by a plurality of angularly extending web members; diametricallyopposed vertical walls integral with said switch actuator extendingbetween the base of said actuator and said annular rim; a guide lug onthe outer side each of said vertical walls; said axially extendingsupport flanges containing guide notches slidably receiving said lugs;the base of said actuator containing an aperture receiving said motorshaft; said lugs in said notches and said vertical walls in conjunctionwith said axially extending flanges all cooperating for concentricallypositioning said basket-shaped switch actuator upon said shaft; a coilspring concentrically positioned about said shaft engaging said supportmember and the base of said switch actuator normally biasing the switchactuator away from said support member into a position engaging thecontacts on said first and second leaf spring members; said verticalwalls of said switch actuator each including spaced shoulders; saidradial flanges of said support member each including spaced axiallyextending lugs; and two weight members each comprising a pair of spacedarcuate fingers engaging said shoulders on said walls and being retainedby said axially extending lugs on said support member whereby apredetermined centrifugal force developed at predetermined motor speedmoves said weights radially outwardly generating an axial force of agreater magnitude than the force of said coil spring positively forcingsaid basket-shaped switch actuator against the force of said coil springmoving said annular rim out of engagement with one of said leaf springmembers permitting positive disengagement of their respective contactsopening the series circuit to said starting winding.